1. Field of the Invention
This invention relates to a key board switch exhibiting click feeling (hereinafter referred to as "clicked key board switch") which is used for a key board or the like and adapted to operate a membrane switch arranged on a patch in a frame due to vertical movement of a key stem provided in the frame, and more particularly to a clicked key board switch constructed so as to reduce deviation between a position at which click feeling is provided and a position at which the switch is turned on.
2. Description of the Prior Art
A key board switch which has been conventionally used for a key board or the like is generally constructed in a manner such that a key stem is vertically movably supported in a frame in which a membrane switch is arranged, resulting in the membrane switch in the frame being operated due to vertical movement of the key stem, as disclosed in, for example, Japanese Utility Model Application Laying-Open Publication No. 168028/1983, Japanese Utility Model Application Laying-Open Publication No. 165623/1987 and Japanese Patent Application Laying-Open Publication No. 80927/1987. In the so-constructed conventional key board switch, a pressing portion which is contacted directly with the membrane switch to operate it generally comprises a separately formed member interposed between the membrane switch and the key stem as disclosed in the Japanese publications mentioned above. Alternatively, it may be integrally formed at a lower portion of the key stem as disclosed in Japanese Utility Model Application Laying-Open Publication No. 133927/1986. Also, the conventional key board switch is often provided with a mechanism for providing a finger of an operator with click feeling in addition to the above-described mechanism for operating the membrane switch, as disclosed in Japanese Utility Model Application Laying-Open Publication No. 193634/1985.
The conventional key board switch in which the mechanism for pushing down the membrane switch is provided separate from the mechanism for providing click feeling has a disadvantage of generating considerable deviation between a position at which the membrane switch is turned on and a position at which click feeling is provided because both mechanisms are separately arranged.
Also, in the conventional key board switch in which the pressing portion is integrally formed at the lower portion of the key stem, the key stem is formed into a shape that its lower side is larger than its top side. This results in an arrangement of the key stem in the frame which requires the insertion of the key stem into the frame from the side of a lower surface of the frame. Accordingly, such construction is not suitable for the automatic assembling of the key board switch, resulting in failing to be accommodated to such a free key layout as employed in a register.